This invention relates to covers, doors or enclosures for air bags.
The present invention generally relates to a door or cover to enclose and protect an air bag and more specifically to an air bag door located on the passenger side of the passenger compartment. Typically a passenger side air bag door or cover is secured to a portion of the instrument panel and is opened by inflation forces generated by the air bag. It is desirable to provide a cover or door which can be opened in response to a relatively low level of air bag deployment forces while still being structurally sound so that it will not break when pushed on by the occupant or when objects are placed upon it. It is an object of the present invention to provide an easy opening air bag door which will not impede deployment of the air bag, or deform in any manner to impact closely space parts such as the windshield. An advantage of providing a door which opens in response to a low level of airbag deployment forces is that less inertia loads are generated on a hinge portion permitting a greater latitude in the design of the hinge. While the preferred embodiment of the invention shows a passenger side air bag door the invention is not so limited. A further object of the present invention is to provide a tear seam in a door constructed of relatively rigid material.
Accordingly, the invention comprises: a cover or door, of integral construction, for an air bag comprising: a panel, hinge means formed between a first side of the cover for enabling the panel to rotate thereabout after the panel separates from a seam in response to forces imparted thereto by an expanding air bag. The seam, interposes an opposite side of the cover and the panel, and provides a tear or crack region along which the panel separates from the opposite side. The seam comprises stress enhancing means for increasing stresses in the material and includes a laterally extending narrow first portion, a closely spaced laterally extending narrow second portion and a thin bridge joining the first and second portions formed in the material forming the seam. The first portion, second portion and bridge are relatively movable one to the other so as to generate in the material at least two zones of increased tensile stress and preferably at least two zones of increased compressive stress sufficient to cause the material to tear. During the inflation of the air bag, the cover is placed in a stressed condition, causing in the preferred embodiment, the relative rotation of the first portion, bridge and second portion, stretching the material in the seam region to its ultimate elongation generally within the zones of increased tensile stress causing such material to initially separate or crack. In response to the continued inflation of the air bag, the crack laterally and rapidly propagates across the width of the seam severing the panel from the opposite side of the cover. This rapid propagation in part results from using a relatively stiff material.
Many other objects and purposes of the invention will be clear from the following detailed description of the drawings.